Based on the underlying compatibility of the production processes (wet laying), “tissue” production is counted among the paper making techniques. The production of tissue is distinguished from paper production by its extremely low basis weight of normally less than 65 g/m2 and its much higher tensile energy absorption index. The tensile energy absorption index is arrived at from the tensile energy absorption in which the tensile energy absorption is related to the test sample volume before inspection (length, width, thickness of sample between the clamps before tensile load). Paper and tissue paper also differ in general with regard to the modulus of elasticity that characterizes the stress-strain properties of these planar products as a material parameter.
A tissue's high tensile energy absorption index results from the outer or inner creping. The former is produced by compression of the paper web adhering to a dry cylinder as a result of the action of a crepe doctor or in the latter instance as a result of a difference in speed between two wires (“fabrics”). In the latter technique, often referred to as “(wet) rush transfer”, for instance the forming fabric of the paper machine is moved at greater speed than that of the fabric to which the formed paper web is transferred, for instance a transfer fabric or a TAD fabric (through air drying), so that the paper web is somewhat bundled when it is taken up by the transfer fabric. Many prior art documents (e.g. EP-A-0 617 164, WO-94/28244, U.S. Pat. No. 5 607 551, EP-A-0 677 612, WO-96/09435) refer to this as “inner creping”, when they describe the production of “uncreped” tissue paper by rush transfer techniques. The inner and outer creping causes the still moist, plastically deformable paper web to be internally broken up by compression and shearing, thereby rendering it more stretchable under load than uncreped paper. Most of the functional properties typical of tissue and tissue products result from a high tensile energy absorption index (see DIN EN 12625-4 and DIN EN 12625-5). Typical properties of tissue paper include the ready ability to absorb tensile stress energy, their drapability, good textile-like flexibility, a high specific volume with a perceptible thickness, as high a liquid absorbency as possible and, depending on the application, a suitable wet and dry strength as well as an interesting visual appearance of the outer product surface.
Softness is an important property of tissue products such as handkerchiefs, cosmetic wipes, toilet paper, serviettes/napkins, not to mention hand or kitchen towels, and it describes a characteristic tactile sensation caused by the tissue product upon contact with the skin.
Although the term “softness” is generally comprehensible, it is extremely difficult to define because there is no physical method of determination and, consequently no recognized industrial standard for the classification of different degrees of softness.
To be able to detect softness at least semi-quantitatively, softness is determined in practice by means of a subjective method. To do so, a “panel test” is carried out in which several trained test persons give a comparative opinion.
In simplified terms, softness can be subdivided into its main characteristics, surface softness and bulk softness. Surface softness describes the feeling perceived when e.g. one's fingertips move lightly over the surface of the sheet of tissue. Bulk softness is defined as the sensory impression of the resistance to mechanical deformation that is produced by a tissue or tissue product manually deformed by crumpling or folding and/or by compression during the process of deformation.
One method for increasing bulk softness of tissue paper as taught by WO 96/25557 involves                a) wet-laying an aqueous slurry containing cellulosic fibres to form a web        b) applying a water soluble polyhydroxy compound to the wet web, and        c) drying and creping the web (wet web addition method).        
It is further known from U.S. Pat. No. 4,764,418 that some humectants such as polyethylene glycol contribute to the softness of tissue products if they are applied to a dry web.
The use of humectants, such as polyhydroxy compounds, in highly concentrated form, as softeners however, has the disadvantage that the humectant may, upon contact, draw too much moisture from the skin, for instance when blowing one's nose with a tissue handkerchief. Moreover the softening effect is not yet satisfactory.
WO 96/24723 teaches increasing the surface softness of tissue paper by applying discrete deposits of a water free lotion composition containing an oil and a wax. Since however, due to its solid consistency, the treatment composition remains on the surface of the tissue paper, it cannot contribute to bulk softness. Further, water-free lotion compositions based on waxy or oily materials often feel unpleasantly greasy or oily.
Moreover, water-free lotions such as the one in WO 96/24723 often do not feel particularly pleasant to the skin which is due to a low moisture content.
EP A 1 029 977 relates to a composition for treating paper products, such as tissue products, comprising between 30 and 90% by weight of oil, between 1 and 40% by weight of wax, between 1 and 30% by weight of an emulsifying agent and between 5 and 35% by weight of water. This lotion composition is solid or semisolid at 30° C. and remains primarily at the surface of the tissue paper, although it penetrates the tissue paper somewhat more than the solid composition of WO 96/24723.
DE 199 06 081 A1 discloses emulsions containing (a) 5 to 25% by weight polyol poly-12-hydroxy stearate, (b) 50 to 90% by weight waxy esters and (c) 5 to 25% by weight waxes. This document further contains examples describing the treatment of tissue papers with W/O emulsions as defined above containing about 20 to 25% water. These compositions are solid or semisolid at 30° C. (example 1 corresponds to lotion F of EP A 1 029 977) and show the same penetration behaviour as described above for the lotions of EP A 1 029 977.
One object of the present invention involves providing a treated tissue paper that overcomes the disadvantages of prior art formulations.
In particular, the present invention aims at providing a tissue paper treated with a lotion composition which remains stable while enhancing softness, in particular, bulk softness of the tissue product.
A further technical object of the present invention is to provide a lotioned tissue paper which feels very pleasant to the skin and is not oily or greasy to the touch.